Shinpei Shibata 柴田　晋平

Yamagata Univ. 山形大学Department of Phys 物理学科

The Structure of the Pulsar Magnetosphere via Particle Simulation with GRAPE

IAUS291 ＠ Beijing 24 Aug 2012

CollaboratorsT. Wada (NAOJ)

S. Yuki (Yamagata U.)M. Umizaki (Yamagata U.)

IAUS291 ＠ Beijing 24 Aug 2012

Summary of our Particle Simulation

1. The outer gap can be reproduced under a few simple assumptions.

2. Centrifugal driven particle acceleration at the top of the closed field region (Y-point) is suggested. E-perp effect.

3. Dead zones along separatrix of the oppositely- directed current is found. PC and SG locate above it and OG below it.

For detail, see Wada, T., Shibata, S., 2011, MNRAS, 418, 612Wada, T., Shibata, S., 2007, MNRAS, 376, 1460Umizaki, M., Shibata, S., 2010, PASJ, 62, 131Yuki, S., Shibata, S., 2012, PASJ, 64, 43

GRAPE-6@nao.jpSpecial purpose computer forAstronomical N-body Problem

Plasmas are represented by several tens of thousands of super-particles.Cal .Domain is 3D (60RL)^3

60RL

60RL

60RL

We iteratively solve the equation of mo. and EM field until steady state is settled down.

1. The outer gap can be reproduced under a few simple assumptions.

(i)The system is axis-symmetric,

(ii) rel. eq. mo. for super particles with radiation drag force.

B-field line

path

Curvature radiation

RadiationDrag force

1. The outer gap can be reproduced under a few simple assumptions. (cont.)

1. (m, q) are chosen so that any plasma drift motions are tracked correctly. dt<< gyro-period

2. Radiation drag force is taken into account in the lowest order approximation.

(iii) Plasma sources are provided for - free emission from NS surface - pair creation if E// > Ec. (on the spot approx.)

Bγ ＋ B e+ ＋ e-

γ ＋ X-ray e+ ＋ e-

Two photon pair creation

Electric field

magnetic pair creation

1. The outer gap can be reproduced under a few simple assumptions. (cont.)

That’s all!!!

model parameter

(*) Central magnet is rotating : i.e. voltage on NS

BC. on NS surface is strictly satisfied, because we use the Green function satisfying the boundary condition to obtain the electromagnetic field.

1. The outer gap can be reproduced under a few simple assumptions. (cont.)

ligh

t cy

lind

er

outer gap

Pairs are continuously produced.

Pairs are immediately separated by the field-aligned electric field.

E// map

Because we have plasma sources, E// is screened out everywhere, except for the outer gap where E// is just above Ec: necessary minimum for pair creation.

ligh

t cy

lind

er

toroidal speed is high, radiation carries off angular momentum from the magnetosphere. Back reaction causes drift across the magnetic field to make out flow.

2. Centrifugal driven particle acceleration at the top of the closed field region (Y-point). E-perp effect.

Open magnetic flux

This outflow is essentially due to strong induction of rotation, (corotation), i.e., E-perp, more basically emf

Map of E/B

（ Uzdensky, 2003 ）

Force-free Udzdenski sol.

light

cylin

der

2. Centrifugal driven particle acceleration at the top of the closed field region (Y-point). E-perp effect. (cont.)

Initial state （ Uzdensky,

2003） Magnetic reconnection takes place

t ～ 4 x 10^5 ⊿ t

Z / RLC

0.99 1.000.00

0.01

0.00

0.01

1.01

0.020.02

R / RLC

Z / RLC

⇒ heating and acceleretion

2-D cylindrical PIC simulation for Y-point.

2. Centrifugal driven particle acceleration at the top of the closed field region (Y-point). E⊥ effect. (cont.)

centrifugal driven reconnection at the top of the closed field region

Map of Non-corotational electric potential

Dead zone

We find another dead zone in the middle latitudes.This dead zone locates on the field lines which separates the outgoing current and ingoing current.

Let us call this zone the current neutral dead zone.

3. Dead zones along separatrix of the current is found. OG, PC locate above it and SG below it.

after Yuki, S., Shibata, S., 2012, PASJ, 64, 43

The outer gap is sandwiched by two dead zones. Therefore, the boundary conditions used previously in the outer gap is correct.

The polar cap and the slot gap would be above the current neutral dead zone.

after Yuki, S., Shibata, S., 2012, PASJ, 64, 43

3. Dead zones along separatrix of the current is found. OG, PC locate above it and SG below it. (cont.)

Summary of Particle Simulation

1. The outer gap can be reproduced under a few simple assumptions.

2. Centrifugal driven particle acceleration at the top of the closed field region (Y-point) is suggested. E-pep effect. Magnetic reconnection.

3. Dead zones along separatrix of the current is found. PC and SG locate above it and OG below it.

For detail, see Wada, T., Shibata, S., 2011, MNRAS, 418, 612Wada, T., Shibata, S., 2007, MNRAS, 376, 1460Umizaki, M., Shibata, S., 2010, PASJ, 62, 131Yuki, S., Shibata, S., 2012, PASJ, 64, 43

A New source of radiation,Fall back particles on to PC,Mode changing etc,,,,,

Strong emf + limited source of plasma

Thank you!